Two functions, rpc_gss_max_data_length() on the client side, and rpc_gss_svc_max_data_length() on the server side, are useful in determining how large a piece of data can be before it is transformed by security measures and sent “over the wire.” A security transformation such as encryption usually changes the size of a piece of transmitted data, most often enlarging it. To make sure that data won't be enlarged past a usable size, these two functions return the maximum pre-transformation size for a given transport.
For more information, see the rpc_gss_max_data_length(3NSL) man page.